England Under-21 boss Aidy Boothroyd has labelled their Slovakia showdown as must win.
The Young Lions head into their second Euro 2017 game on Monday after Friday's opening 0-0 draw against holders Sweden.
Defeat would leave their Group A qualification hopes hanging by a thread with leaders Slovakia having already beaten hosts Poland 2-1 on Friday.
Only the group winners and best runner-up from the three pools go through to the semi-finals and Boothroyd knows England cannot afford to let Slovakia get out of sight.
He said: "It's knockout football now without a doubt. We've got to win and then win and win the next one after that. But we have to beat the Slovakians first.
"They have had a brilliant start. They're a very good team and I've been really impressed with them. Their game with Poland was probably better to watch than our game with Sweden and it will be difficult. We totally respect the result they got.
"We have to go full pelt for every game but at the same time because of the squad that we've got I've got to think about using everyone that's in it.
"But we have to win so I've got to pick the best team, even if some of them might be a bit tired they might have to play a smaller part in the game and think about what goes on in the last half hour of the game."
Senior boss Gareth Southgate, assistant Steve Holland and technical director are all in Kielce after arriving for the Sweden game on Friday.
Southgate watched training on Sunday and Boothroyd believes it shows the players there is an opportunity to step up to the senior side.
"It's really helpful having them here. It's great that Gareth, Steve and Dan are here because it shows players there is a pathway for them," he said.
"And if the senior manager can take time out of his busy schedule to come to watch us then it gives the players a boost. Gareth's been very positive. We are very close anyway.
"It's great, if I have any questions about players Gareth can be my sounding board because he knows them all so well and was with them in Toulon."